The Diabetic Retinopathy Clinical Research Network (DRCRnet) was formed to conduct clinical trials and epidemiological studies for diabetic retinopathy. As part of the establishment of the network, it is necessary to standardize data collection methods, testing procedures, and treatment techniques for use in the anticipated multiple protocols to be conducted by the network. One of the treatment techniques requiring standardization is laser photocoagulation treatment of diabetic macular edema. To accomplish this goal, a protocol has been developed to enroll patients with diabetic macular edema who require laser treatment. Procedures to be conducted by standardized protocols include refraction,1 visual acuity testing, fundus photography, fluorescein angiography, optical coherence tomography (OCT) and laser photocoagulation One of the benefits from having a structured protocol will be that the outcome data using the standardized techniques can be used for sample size estimations in future protocols. This is particularly true for OCT for which we need to develop standard methods to assess changes in groups of patients and for which there are limited longitudinal data, especially in groups of patients. The conduct of this study provides the opportunity not only to collect data on a standardized laser protocol commonly used in current clinical practice but also to collect pilot data evaluating a new laser technique. The 'current practice' laser protocol, modified from the ETDRS treatment protocol, involves focal/grid photocoagulation to areas of macular thickening with leaking MA, diffuse leakage or nonperfusion (modified-ETDRS technique). There is extensive evidence supporting the efficacy of ETDRS laser photocoagulation technique for the treatment of macular edema. The alternative technique, called mild macular grid (MMG) photocoagulation, provides mild grid treatment using small, widely separated burns to the retina from 500 to 3000 microns (3500 microns temporally) from the macular center. This technique may potentially have fewer side effects, different edema resolution rate or prevention of future development of macular edema as discussed below. The study will use randomization to assign each patient to receive one of the two treatment methods.